A water repellent layer at a predetermined depth under the ground may be generally utilized in two ways: to prevent the escape of water into the ground from irrigated soil, from water reservoirs, fish raising ponds and the like as well as to prevent underground water from rising above a desired level under specific areas such as roads, airfield landing strips or even in residential areas.
There are known several methods of subterranean waterproofing. The most common one in use is carried out by spraying the area with material such as tar, cement or the like, or penetrating the soil with sprayers and effecting the desired waterproofing by means of a subterranean spraying. Another method is to spread a waterproof medium, such as plastic sheets onto the ground and cover it with soil. Alternatively the sheet may be spread subterraneously by means of a device which is described in Israel Patent No. 51969. The main disadvantage of the latter method resides in its incapability of spreading sheets in contact with each other such as to form an overlap and a watertight surface. Additionally, in order to perform the waterproofing at a reasonable depth, the device must be very powerful and even so sometimes the task cannot be achieved due to unexpected below ground obstacles such as rocks, plant roots and the like.
Israeli Patent No. 58 712 suggests a method and a device for laying strips of flexible sheet material under the ground which method does not require the ground soil to be first removed wherein the applicator is positioned below ground level. In addition to the aforementioned disadvantage of subterranean operation it is not believed that such a substantially "blind" attempt of waterproofing on area can be satisfactorily achieved.